{"id":"F2005L02784","name":"AD/DHC-8/46 Amdt 4 - Cockpit Door Alternate Release","slug":"ad-dhc-8-46-amdt-4-cockpit-door-alternate-release","collection":"legislative_instrument","jurisdiction":"commonwealth","status":"in_force","isInForce":true,"actNumber":null,"makingDate":null,"administeringDepartment":null,"currentVersion":{"id":37682,"registerId":"commonwealth-F2005L02784-current","compilationNumber":null,"startDate":"2026-04-01","status":"InForce","reasons":null,"registeredAt":null},"sections":[{"sectionNumber":"Bombardier (Boeing Canada/De Havilland) ","sectionType":"division","heading":"Bombardier (Boeing Canada/De Havilland) DHC-8 Series Aeroplanes","content":"### Bombardier (Boeing Canada/De Havilland) DHC-8 Series Aeroplanes\n\n| AD/DHC-8/46 Amdt 4 | Cockpit Door Alternate Release | 11/2005 |\n| ------------------ | ------------------------------ | ------- |\n\n| Applicability: | DHC-8 aircraft Models 102, 103, 106, 201, 202, 301, 311, 314, and 315; equipped with cockpit door assembly, part numbers 82510074-( ), 82510294-( ),82510310-001, 8Z4597-001, H85250010-( ), 82510700-( ), or 82510704-( ); except 82510704-502 and 82510704-503.Note 1: -( ) denotes all dash numbers.                                                                                                                                                                                                                                                                                                                                                                                           |\n| -------------- | ------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- |\n| Requirement:   | 1. Action in accordance with Section III, Accomplishment Instructions, “Special Inspection/Repair”, of de Havilland Service Bulletin (SB) 8-52-39 Revision B, dated 4 July 1997, or a later Transport Canada approved revision.2. Install Modification 8/2337 in accordance with SB 8-52-39 Revision B, or a later Transport Canada approved revision.Note 2: Modifications 8/2228, 8/2229, 8/2231, 8/2232, 8Q100859, 8Q900267, 8Q420101, 8Q420143, 8Q200131, or 8Q420440, installed during production are equivalent to Modification 8/2337, with respect to the cockpit door alternate release mechanism, and meet the intent of Requirement 2.Note 3: Transport Canada AD CF-1996-20R4 refers. |\n| Compliance:    | 1. Before 31 October 1997. Inspect thereafter at intervals not to exceed 800 flight hours.2. Before 31 October 1997.The compliance times remain unchanged by this issue of the Directive.                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                         |\n|                | This Amendment becomes effective on 27 October 2005.                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                              |\n| Background:    | Investigation by the manufacturer of an in-flight incident of failure of the cockpit door alternate release mechanism has revealed a serious design deficiency. This Directive requires incorporation of a modification to correct the design deficiency.Amendment 1 extended the compliance time. An All Operator Message from the manufacturer gave further instructions to operators regarding a redesign of the door hinges because the existing modification was not satisfactory under all conditions.                                                                                                                                                                                      |\n\n|     | Amendment 2 again extended the compliance due to further difficulty with the modification, and introduced a post mod repetitive inspection, which will deal with the shortcoming of the modification until such time as terminating action is determined.Amendment 3 amended applicability due to the installation of new reinforced cockpit doors.Amendment 4 is issued in response to a revision of the related Transport Canada AD, which amends applicability to exempt new reinforced cockpit doors that are not subject to the alternate release jamming issue. |\n| --- | --------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- |\n\n![](image.001.png)  \nDavid Villiers  \nDelegate of the Civil Aviation Safety Authority\n\n15 September 2005","sortOrder":0},{"sectionNumber":"AD/DHC-8/46 Amdt 4","sectionType":"part","heading":"AD/DHC-8/46 Amdt 4","content":"## AD/DHC-8/46 Amdt 4","sortOrder":1},{"sectionNumber":"Cockpit Door Alternate Release","sectionType":"part","heading":"Cockpit Door Alternate Release","content":"## Cockpit Door Alternate Release","sortOrder":2},{"sectionNumber":"11/2005","sectionType":"part","heading":"11/2005","content":"## 11/2005","sortOrder":3}],"analysis":{"flash_summary":{"complexity_score":5,"scope_assessment":{"changed":true,"description":"Yes. The instrument has evolved from a broad requirement to inspect and modify cockpit door alternate‑release mechanisms on a range of DHC‑8 types to a narrower scope in Amendment 4: it exempts newer reinforced cockpit doors that are not subject to the alternate‑release jamming issue. Earlier amendments changed compliance timing and added repetitive inspections as an interim measure; Amendment 4 specifically adjusts applicability to align with a revised Transport Canada AD and remove aircraft fitted with reinforced doors from the mandated population."},"complexity_factors":["Detailed applicability list with multiple aircraft models and a long list of cockpit door part‑number ranges","Specific exclusions of two dash numbers (82510704‑502 and ‑503) within an applicability clause","Cross‑references to a manufacturer Service Bulletin (SB 8‑52‑39 Revision B) and any later Transport Canada approved revisions","Multiple notes recognizing a number of different production modification numbers as equivalent to the required modification (creates equivalence mapping)","History of prior amendments that altered compliance timing and introduced repetitive inspections (adds conditional history to interpret)","Compliance instruction combining a past due initial compliance date (31 Oct 1997) with a recurring inspection interval (800 flight hours) and an amendment effective date (27 Oct 2005) — potential for reading confusion","Reference to an external Transport Canada AD (CF‑1996‑20R4) for related regulatory context","Requirement to follow a specific section of the Service Bulletin (Section III), not a single straightforward instruction (technical procedural dependency)"],"plain_english_summary":"**What this directive does (mechanically)\n\n- Requires operators of specified De Havilland (Bombardier/De Havilland) DHC‑8 (Dash 8) aeroplanes to inspect and, where necessary, modify the cockpit door alternate‑release mechanism.\n- The inspection and modification must be carried out in accordance with Section III, \"Special Inspection/Repair\", of de Havilland Service Bulletin (SB) 8‑52‑39 Revision B (or a later Transport Canada approved revision). [Requirement 1]\n- Where required, operators must install Modification 8/2337 per the same service bulletin; a list of earlier production modifications are accepted as equivalent to 8/2337 for the alternate‑release mechanism. [Requirement 2; Note 2]\n\nWho the rule applies to\n\n- Applies to DHC‑8 models 102, 103, 106, 201, 202, 301, 311, 314 and 315 fitted with certain cockpit door assemblies (specific part‑number ranges listed). Two specific dash numbers of one door part (82510704‑502 and ‑503) are excluded from the applicability. [Applicability]\n- Amendment 4 further exempts newer reinforced cockpit doors that are not subject to the alternate‑release jamming problem (it narrows applicability to exclude those doors). [Background / Amendment 4]\n\nKey timing and repeat requirements\n\n- The original required action timeline was \"before 31 October 1997\" for initial compliance. After the initial action, inspections are to be repeated at intervals not exceeding 800 flight hours. [Compliance]\n- The Directive text notes that the compliance times remain unchanged by this issue of the Directive; the Amendment 4 instrument itself became effective 27 October 2005.\n\nWhy the regulator issued this directive (official rationale)\n\n- The manufacturer found an in‑flight failure of the cockpit door alternate‑release mechanism and described it as a serious design deficiency. The directive's stated purpose is to correct that deficiency by inspection and modification. [Background]\n- Earlier amendments extended compliance dates and introduced a repetitive inspection after the modification because the first modification did not fully eliminate the problem in all conditions. Amendment 4 aligns applicability with a revised Transport Canada AD and exempts certain reinforced doors.\n\nPractical impacts, costs and incentives\n\n- Who pays: aircraft owners/operators pay for the inspections, modifications, parts and associated aircraft downtime. [Requirement, Compliance]\n- Who decides: the Civil Aviation Safety Authority (via this Directive) mandates the actions; the modification and inspection procedures are specified by the manufacturer’s Service Bulletin and any later Transport Canada‑approved revisions. Operators must follow those documents or newer approved revisions. [Requirement]\n- Behaviour change: operators must add the special inspection to maintenance schedules and, where necessary, install the modification or rely on an equivalent production modification already fitted. They must also keep to the 800 flight‑hour inspection interval after modification. [Compliance; Note 2]\n- Concentrated benefits vs diffuse costs: the safety benefit accrues to flight crews and passengers on affected aircraft (concentrated safety gain per aircraft), while the direct costs (parts, labour, ground time) are borne by the operator (diffuse across fleet operators). The directive permits certain previously installed production modifications as meeting the requirement, concentrating compliance relief on operators that already fitted those mods. [Requirement; Note 2]\n- Trade‑offs and opportunity costs: operators trade maintenance cost and aircraft downtime for reduced risk of cockpit door alternate‑release failure. Some operators with newly reinforced doors may be exempted, which reduces their cost and operational disruption. [Amendment 4]\n- Implementation risk and compliance burden: the requirement references a specific service bulletin and allows only Transport Canada approved later revisions; operators must track revisions and the equivalence of multiple modification numbers, which adds administrative and technical complexity. The presence of multiple amendment histories and prior extensions indicates some practical difficulty with the initial fix. [Requirement; Notes; Background]\n\nConcrete operational notes\n\n- Several production modifications (8/2228, 8/2229, 8/2231, 8/2232 and other 8Q‑ numbers listed) are explicitly accepted as equivalent to Mod 8/2337 for the alternate‑release mechanism; operators who already have those mods fitted do not need to install 8/2337. [Note 2]\n- The directive cross‑references a Transport Canada AD (CF‑1996‑20R4) and relies on Transport Canada approval for later service bulletin revisions. [Note 3]\n\nSource mechanics vs source claims\n\n- The directive states its safety purpose (manufacturer’s investigation found a design deficiency). That is the claimed benefit. The concrete mechanisms to achieve that benefit are mandated inspections, a specific modification or accepted equivalent production mods, and recurring inspections (800‑flight‑hour interval). The costs (parts, labour, downtime), administrative burden (tracking service bulletin revisions and equivalence of mods), and the potential for interim inspection regimes until a terminating action is found are all explicit trade‑offs embedded in the text.\n"},"kimi_summary":{"content_quality":"ok","complexity_score":4,"scope_assessment":{"changed":true,"description":"The original directive addressed a cockpit door alternate release design deficiency. Over four amendments, the scope has expanded significantly: (1) compliance times were repeatedly extended as the modification proved difficult, (2) a recurring inspection requirement was added as interim mitigation when the modification proved insufficient, (3) applicability was expanded to cover new reinforced cockpit doors, then (4) narrowed again to exempt specific new door part numbers that don't share the jamming vulnerability. The directive has evolved from a simple 'fix it' order to a complex regime of inspections, modifications, equivalencies, and conditional applicability based on door design evolution."},"complexity_factors":["Multiple amendment history (Amendment 4) with layered background explaining evolution of the problem and previous fixes","Specific part number applicability with dash number wildcards (-( )) and explicit exemptions (82510704-502 and 82510704-503)","Cross-reference to external documents: Transport Canada AD CF-1996-20R4 and de Havilland Service Bulletin 8-52-39 Revision B","List of 10 equivalent production modifications that satisfy the requirement (Modifications 8/2228, 8/2229, etc.)","Dual compliance structure: immediate inspection with recurring 800-hour intervals AND one-time modification installation","Conditional logic in applicability (equivalency determinations for factory-installed mods vs. post-production mods)"],"plain_english_summary":"This Airworthiness Directive requires owners/operators of certain Bombardier DHC-8 (Dash 8) models with specified cockpit door parts to inspect the cockpit door alternate release (repeat every 800 flight hours) and install a mandated modification to fix a design defect that can cause the alternate release to jam. Aircraft with newer reinforced door parts (P/Ns ending -502 and -503) are exempt. The rule prevents scenarios where rescuers or crew cannot open the cockpit in an emergency."},"flash_summary_failed":{"failed":true,"reason":"Unauthenticated. Configure AI_GATEWAY_API_KEY or use a provider module. Learn more: https://ai-sdk.dev/unauthenticated-ai-gateway","source":"analysis-cron"}},"importantCases":[],"_links":{"self":"/api/acts/ad-dhc-8-46-amdt-4-cockpit-door-alternate-release","history":"/api/acts/ad-dhc-8-46-amdt-4-cockpit-door-alternate-release/history","analysis":"/api/acts/ad-dhc-8-46-amdt-4-cockpit-door-alternate-release/analysis","conflicts":"/api/acts/ad-dhc-8-46-amdt-4-cockpit-door-alternate-release/conflicts","importantCases":"/api/acts/ad-dhc-8-46-amdt-4-cockpit-door-alternate-release/important-cases","documents":"/api/acts/ad-dhc-8-46-amdt-4-cockpit-door-alternate-release/documents"}}